Ambient temperature compensating means for automatic circuit breakers



Aug. 5, 1952 E. BESAG ET AL 2,606,062

AMBIENT TEMPERATURE COMPENSATING MEANS FOR AUTOMATIC CIRCUIT BREAKERSFiled Aug. 12, 1948 2 SHEETS-SHEET l lrmen! (5W ufazam 744222 Mam TIME 5C M 1 (5MALA/UZL/ Attor'neyi Aug. 5, 1952 E. BESAG AL 2,606,062

AMBIENT TEMPERATURE c ENSATING MEANS FOR AUTOMATIC CIRCUIT BREAKERS 2SHEETS--SHEET 2 Aug 12 W lllumm 'i fi 5M 9 y I I Attorney;

Patented Aug. 5, 1952 AMBIENT TEMPERATURE COMPENSAT- ING MEANS FORAUTOMATIC CIRCUIT BREAKERS Ernst Besag and Walter Edward Hill, Streetly,

and Thomas Daniel Guy Wintle, Walsall, Eng- 7 land, assignors to' J. A.Crabtrce & Co. Limited, Walsall, S-tafiordshire, England, a British com-Application August 12, 1948, Serial No. 43,824

- In Great Britain August 14, 1947 This invention relates toimprovementsin the trip mechanism of automatic circuit breakers andsimilar electrical switchgear, and is particularly '1 Claims. (Cl.297-45) concerned with mechanism, operated by thermal release overloaddevices, and which provides ambient temperature compensation, for usewith motor protective switches.

According to this invention, a rotationally adjustable member is formedwith a cam adapted for adjusting the ambient temperature compensatingmeans which is engageable by the trip mechanism upon the occurrence ofoverload conditions. Such ambient temperature compensating means may bein the form of a bimetallic blade adapted to be rocked in see-sawfashion upon the stem of an adjusting screw, so that the gap between theblade and the trip mechanism may be varied.

In order to enable the invention to be readily understood, referencewill now be made to the accompanying drawings illustrating, by way ofexample, one construction for carrying the invention into efiect, inwhich drawings:

Figure 1 is a perspective view of a casing for the ambient temperaturecompensating means of our present invention, showing the same mounted onthe end of an overload box. p

Figure 2 is a plan view of the device shown in Figure 1, the cover ofthe casing having been removed to disclose the interior mechanism.

Figures 3 and 4 are sectional views on the lines I1'IIII and IV-IV,respectively; of Figure 2, with the cover mounted in position.

Figure 5 is a sectional view on the line V-V of Figure 3.

Figure 6 is a sectional view on the line VI-VI of Figure 4.

Referring to the drawings, a cap or sleeve (1 is rotationally adjustableon a boss b upstanding from an insulating box casing c secured to a backplate I by bolts 2, which casing houses thermal overload release devices(not shown), which devices are operative to actuate a trip bar m. For amore complete understanding of the construction and operation of thepresent invention, reference is made to our Patents 2,523,897 ofSeptember 26, 1950', relating to Thermal Overload Release Device forAutomatic Circuit Breakers, and 2,527,907 of October 31, 1950, relatingto Automatic Circuit Breaker Having Thermal Overload Release Units, inwhich patents there is an adequate disclosure of thermal overloadrelease devices, particularly trip bars and their associated mechanismscorresponding to the trip bar m of the present invention. The

cap a is formed on its upper surface with a cam d engageable by one endof a bimetallic blade e which serves as a means for compensating forambient temperature, and around said cap is arranged a part cylindricalmetal clip or'sleeve having graduations or markings thereon whichco-operate with a fixed pointer g on the cover h of the casing c forindicating the setting ofthe device.

Inside the cap a, a bow-shaped blade spring i is provided, which springis disposed parallel to the axis of the boss I) in a narrow slot 7c inthe latter. For the purpose of locating the spring i, its inwardlyextending ends are engaged in recesses k in the ends of the boss I). Thespring i acts for taking up tolerances'between the cap a and its bearingon boss b, and for frictionally retaining the cam d in any desiredposition.

A small outwardly-projecting stop c on the boss b, has abuttingengagement with a complementary inwardly-projecting luga on the cap afor the purpose of limiting rotational adjustment of the latter ineither direction of rotation.

The end of the bimetallic blade e remote from the cam, is adjustable inrelation to the trip bar m, and for this purpose, said blade is actedupon between its ends by any suitable adjusting means. According to oneexample, a screw n, seated by spring pressure in a semi-cylindricalthreaded groove 0 in the casing c, is operated so that a shoulder 11.thereon is pressed against the face of the blade e so that the gap asbetween the end of said blade and the end oftrip bar m may be varied. ,1

For imparting guidance to screw 11, areduced stem n on said screw mayextend freely through an opening in the blade 6 and into an opening 0 inthe casing c. The screw n, which may be held in the threaded groove 0 ofthe casing c by a spring blade p of right-angled shape, extends throughan opening in the longer arm p of said spring blade the other spring armp of said spring blade being engaged beneath a shoulder c of the casingc for stressing said spring. The downward thrust exerted by the springblade p on the screw 11. not only serves to keep said screw seated inthe semi-cylindrical threaded groove 0, but also serves to maintain saidscrew in its various positions of adjustment. The kerfed, outer end ofscrew n is accessible through an opening h in the cover h, this openingbeing closed by a spring clip 1' when adjustment has been efiected. Theclip 1', which prevents unauthorized access to the adjusting screw n, isbent to extend over the opening h in the end of the casing, one end ofsaid clip being engageable in a groove 3 in the bottom of the casing c,and the other end having a small circular opening which is pressed overa stud t on the top of; the cover It for retaining the latter in place.

After initial adjustment of the bimetallic blade c has been effected inthe factory by turning the screw n, subsequent adjustment may be made byrotating the knurled cap a and cam 1' o as to rock the blade e upon thestem n for variation of the gap :0.

Having thus described our invention, we claim:

1. An ambient temperature compensating means for automatic circuitbreakers of the thermal overload release type which include tripmechanism and a trip bar for actuating said mechanism, said compensatingmeans comprising an elongated bimetallic blade; a casing enclosing saidambient temperature compensating means;

said casing having an opening through a wall thereof and having athreaded, substantially semi-cylin rical groove on. a p t h r of nalignment with said opening; a screw in threaded engagement with saidgroove and passing transversely through an opening in the intermediateportion of said blade; means operatively engaging said screw to retainsaid screw in engage,- ment with said groove, said screw constituting apivotal mounting for said blade and having a shoulder thereon engageablewith said blade whereby rotation of; said screw will move said bladelaterally to Very the position of its pivotal mounting, one end of saidblade being normally spaced from an end of the trip bar of the circuitbreaker but engageable by said end of said trip bar upon the occurrenceoi overload conditions; and adjusting means en agin he othe end o saidblade to rock the same about said screw to vary the spacing between thefirst-mentioned end of said blade and said one end of said trip barindependently of the position of the pivotal mounting of said blade.

2. An ambient temperature compensating means as defined'in claim 1 inwhich the casing is provided with a second opening in axial alinementwith the first-mentioned opening, and in which an end of said screwenters said second opening whereby said screw is guided in its axialmovements.

3. An ambient temperature compensating means as defined in claim 1 inwhich the casing is provided with a second opening of lesser diameterthan that of said first-mentioned opening and in axial alinementtherewith, and in which said screw has a reduced terminal portion whichenterssaid second opening wherebysaid screw is guided in its axialmovements.

4. An ambient temperature compensating means for automatic circuitbreakers of the thermal overload release type which include tripmechanism and a trip bar for actuating such mechanism, said compensatingmeans comprise ing an elongated, bimetallic blade; a casing en closinsaid ambi n t mperatu e c mp nsatin mea aid casing havin a p i g thr u ha wall thereoi and having a threaded, semi-cylindrioal groove on aportion the in align ment with said opening; a screw in threadedengagement with said groove and passing transversely through an openingin the intermediate portion of said blade, said screw constituting apivotal mounting for said blade and having a shoulder thereon engageablewith said blade whereby rotation of said screw will move said bladelaterally to vary the position of its pivotal mounting, one end of saidblade being normally spaced from an end of the trip bar of the circuitbreaker but engageable by said end of said trip bar upon the occurrenceof overload conditions; adjusting means engaging the other end of saidblade to, reel; the same about said screw to vary the spacing betweensaid first-mentioned end of said blade and said end of said trip barindependently of the position of the pivotal mounting of said blade; andan L-shaped spring having an aperture in one arm thereof through whichsaid screw passes and the other arm of which resiliently engages. s idcas n o keep a d sc contact wi h the semiyl ndrical threa ed groo e insa easing:

5-. an ambient empera ure compensating m ans r aut mat circui breaker oih t ermal ove load. release type hich inohldes. trip mechanism a a p baf r actuatin sllol mechanism said ompensa ing means oom ing an elongted! bimeta lic blade pivotally m unted. intermed ate its e ds, ne end fsai bla e be ng normall spaced irom an. end o th t ip bar o he circuibreaker but eneag ble y sa end o sai rip ar pon th o eno of overloadconditions; a casing enclosing said ambient tempera re compe sa ing mens; a boss project ng i wardly oi s d ca ing; a cap r tatab y moun ed sad bo s; and a cam on said cap and rotatable therewith, saidocam ene s nge h r endo s id lade to roc the l de about its piv ta moun ng to vary hspacing between, the fi -m n ioned nd oi said b a e nd s id end of s idr p b n 6. An ambient temperature compensating means s d fin d in cla min wh h apo n is p s t ed on the casin and i wh ch e cap s p d d w thmarkings, coop ration b e n said pointer and markings indicating theposition o a d am An ambi nt. emp a ure comp nsa in means as definedinrclairn 5 in which a bow, shaped pr ng is. dispo ed par l el to he sof the boss in a narrow slot in said boss and has its intermediate bowedpor ion ir oti idllv engag ng t e in er r o sa d cap:

ERNST BESAG. WALTER EDWARD HILL. THOMAS DANIEL GUY R FERENCES CI ED Thefollowing references are of record in the file of this patent:

UNITED STATES. PA'I'ENTS Fet e s-so-rms-o-f-s Sept 8, 1 .2

